How much does a tankless water heater cost to install?
A tankless water heater costs about $1,200–$4,000 installed before upgrades. Converting from a tank often adds a larger gas line and new venting, putting the total at roughly $2,500–$5,300.
Cost guides put tankless installs at $1,200–$4,000, with gas units at the higher end and an average near $2,800–$3,500. Labor alone runs about $750–$2,300 nationally. Those figures assume the gas line, venting and drain can handle the new unit.
Converting from a tank is where costs climb: upsizing the gas line from ½″ to ¾″ runs $400–$800, new venting $400–$800, and condensing units need a condensate drain. No cost guide prices the whole conversion, so the $2,500–$5,300 range is built from those line items; owners in recent threads reported $4,500–$4,900. Replacing an existing tankless with another should cost less, and installers put a simple swap at $3,500–$5,000.
Confidence: multi-source · Based on 7 cited sources.
Sources
- How Much Does Tankless Water Heater Installation Cost? · This Old House
- How Much Does Water Heater Installation Cost in 2026? · Fixr
- Tankless Water Heater Installation Costs In 2026 · Home Grail
- Tankless water heater installation cost · Thumbtack
- Condensing vs. Non-Condensing Tankless Water Heaters · Navien
- My water heater gave out and my quotes seem unusually high · Reddit
- Tankless water heater quotes · Reddit
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Water Heater Replacement Cost: What a Fair Quote Looks LikeBy Purchasd Research. We compared installed-cost ranges from seven ad-supported cost guides (This Old House, Fixr, PickHVAC, Modernize, Home Grail, Thumbtack and Bob Vila), one completed-install dataset (Rewiring America’s analysis of over 1,200 California heat pump water heater installs), published permit fees from three local governments, code text from a Utah utility district and the California statute, ENERGY STAR and DOE technical guidance, and manufacturer pages for lifespan and repair advice. We read seven Reddit threads from November 2025 to September 2026 in full, recording only prices commenters actually stated. Cost-guide ranges were treated as published estimates, not measurements, and Reddit prices as self-reports. Home Depot and Lowe’s pages block automated reading, so their terms come from search excerpts and are marked unverified. Purchasd received no payment, referral fee or consideration from any manufacturer, retailer, plumber or cost-guide publisher for this research. Most cost guides earn from contractor leads or product sales, This Old House’s headline figures come from Home Depot data, and the manufacturers quoted sell replacement units; each source is labeled by bias. Purchasd has not obtained or tested quotes itself.